Mutate ifelse chain not working for some source variables

I want to create a new variable out of two source variables using the combination mutate and ifelse as follows:

data<-mutate(data,combi_1=ifelse(medicine_1==7 & medicine_2_1==8,221,
                       ifelse(medicine_1==3 & medicine_2_1==224,210,
                              ifelse(medicine_1==2 & medicine_2_1==226,229,
                                    ifelse(medicine_1==3 & medicine_2_1==183,233,
                                          ifelse(medicine_1==157 & medicine_2_1==225,231,
                                                  ifelse(medicine_1==225 & medicine_2_1==157,231,
                                                          ifelse(medicine_1==219 & medicine_2_1==193,230,
                                                                 ifelse(medicine_1==193 & medicine_2_1==219,230,
                                                                         ifelse(medicine_1==219 & medicine_2_1==198,232,
                                                                                 ifelse(medicine_1==198 & medicine_2_1==219,232,NA)))))))))))

The same code was used for 9 "combination_generic_x" and "combination_generic_x_x" variables to create nine "combi_x" var. However, the third time ("combi_3") I got a new empty column. I ran it for "combi_4" and It worked. Why is this selective malfunctioning? The format of the variable is "Character". The source variables(medicine_3 and medicine_3_1) for "combi_3" have less than 10 values. Thanks!